1. Field of the Invention
The present invention relates to a display system for a camera which can display information by rotationally driving an indicator pointer over a scale plate.
2. Description of the Related Art
A display apparatus for a camera which is capable of displaying information by rotationally driving an indicator pointer over a scale plate is per se known. With such a type of display apparatus there are typically provided separate rotating indicator pointer type display devices, each for displaying a particular item of information related to photography, such as iris aperture, photographic distance, film frame number and the like; and each of these display devices includes a rotating indicator pointer which is rotated by the operation of a stepper motor so as to display the corresponding item of information. Further, there is typically provided within the viewfinder of the camera a liquid crystal type display device which displays shutter speed and the like, and it is possible for the photographer to be apprised of such information simply by peeking through the viewfinder and looking at the liquid crystal type display device.
However, the information which is required to be displayed upon a liquid crystal display device is transmitted to the display device in the form of drive signals for the various segments thereof, and those of the segments to which drive signals are supplied for turning them on are turned on with hardly any time delay, whereby the information is displayed as required almost instantaneously. On the other hand, with a display device of the rotating indicator pointer type, the information which is required to be displayed is transmitted to the display device in the form of a pulse signal for rotationally driving the stepper motor for the indicator pointer thereof according to the number of pulses which this pulse signal contains, and the indicator pointer is rotated according to the number of pulses in this input pulse signal, so as to display the required information. Accordingly, in comparison with a liquid crystal type display device, such a rotating indicator pointer display device suffers from a certain time delay in displaying the required information, this time delay being the time period which is required for the indicator pointer to rotate from its initial position to a position appropriate to indicate the current value of the required information. Moreover, a liquid crystal type display device can be termed a display device of the so called electrical type, while by contrast a rotating indicator pointer display device can be termed a display device of the so called mechanical type.
These types of display device are usually controlled with a microcomputer, and the information which is to be displayed is output from the microcomputer to the display device in a previously determined upon order and format. However, since with a display apparatus for a camera according to the prior art no account was taken when performing display control of the delay time periods inherent in the operation of the various types of display device, therefore in displaying information simultaneously both upon a liquid crystal type display device and also upon a rotating indicator pointer display device the problem arose that, when the information which was to be displayed was output to the rotating indicator pointer display device before it was output to the liquid crystal type display device, it took a certain time period to output the pulse signal representing the display information to the rotating indicator pointer display device, and until the output of this pulse signal was completed it was not possible even to start to output the control signal for the liquid crystal type display device. Therefore, display of the information which was to be displayed upon the liquid crystal type display device was delayed by the full time period required for the indicator pointer of the rotating indicator pointer display device to be rotated to its position to display the information required to be displayed thereby.